Printed circuit boards (PCBs) are commonly found in a variety of electronic devices, including computers, televisions and mobile devices. PCBs commonly include capacitors mounted to the PCB in order to perform a variety of functions. A capacitor can include two conductive plates separated by a dielectric such as ceramic. Certain classes of ceramic capacitors can exhibit a characteristic called piezoelectricity that can cause an internal generation of a mechanical strain in the ceramic resulting from an applied electrical field. The magnitude of the generated strain can be proportional to the strength of the electrical field, or the voltage difference applied across two conductors placed on either end of the ceramic material. When the capacitor is placed in an AC circuit, the ceramic within the capacitor can expand and contract at a frequency approximately equal to that of the AC supply.
This motion can cause several problems. First, if a capacitor is mechanically coupled to a membrane such as a PCB, these expansions and contractions can apply a periodic force on the PCB. As a result, the entire PCB can vibrate at a harmonic frequency of the power supply. The effect can be particularly pronounced when the driving frequency is approximately equal to the resonate frequency of the PCB. The vibration of the PCB can also create acoustic sound waves. In some situations, the resulting sound waves can have enough amplitude to be heard by a user of a device. Secondly, excessive vibrations can weaken solder joints and other electrical connections on the PCB, increasing the likelihood that the device will fail.
Therefore, what is desired is a reliable way to mechanically couple a capacitor to a PCB while reducing an amount of vibrational energy that is transferred from the capacitor to the PCB.